Process of melt spinning and stretching filaments by passing them through liquid drag bath



Oct. 3, 1961 J J KILIAN PROCESS OF MELT sPIN'NIiq BY PASSING THEM THRO Filed Nov. 28, 1958 ZZZ (5.1

3,002,804 AND STRETCHING FILAMENTS UGH LIQUID DRAG BATH 5 Sheets-Sheet 1 Eig- 4 IN VENTOR J OSEPH J. KILIAN ATTORNEY 3,002,804 FILAMENTS BATH Oct. 3, 1961 J. J. KILIAN PROCESS OF MELT SPINNING AND STRETCHING BY PASSING THEM THROUGH LIQUID DRAG Filed Nov. 28, 1958 3 Sheets-Sheet 2 0 W a w w u 7 M W WWW mm 9 R o A m w w R 0 n w e N N uA 041m E' N CL ..r o wmmu W lrtol. WH M ll w 0 0 0 2 0 0 W 3 7. O 9 n0 7 6 5 4 1a 2 I. 0

IINDUP SPEED YPH.

IN VENTOR JOSEPH J. KILIAN ATTORNEY Oct 3 1961 J. J. KILIAN 3 002 8 PROCESS OF MELT SPINNING AND STRETCHING FILAMENT 04 BY PASSING THEM THROUGH LI UID DR Flled Nov. 28, 1958 Q AG fSheets-Sheet 3 Eig.6'a

SAMPLEI 40 DENIER-H FILAIENT mu own In uouw am ss I |I|||| ||so sum: 40 DENlER-l3 FILAHENT YARN own on com PIN loo- 2 I so E l HODULUS AT 4% STRETCH, GRAMS PER DENIER I I I I I I X l l l l l I l l 0 I0 I00 PERCENT YARN on TEST PACKAGE INVENTOR JOSEPH J. KILIA ATTORNEY United States Patent 3,002,804 PROCESS OF MELT SPINNING AND STRETCI-IING FILAMENTS BY PASSING THEM THROUGH LIQUID DRAG BATH Joseph J. Kilian, Covington, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed Nov. 28,1958, Ser. No. 777,545 SClaims. (Cl.18--54) This invention relates to an improved process for preparing oriented filaments from synthetic linear polymers. More particularly, this invention relates to drawing meltspun synthetic linear polymer filaments.

This application is a continuation-in-part of copending application Serial No. 634,209, filed January 15, 1957.

It is well known that useful filaments can be produced by the melting of synthetic linear polymers and extruding the melt through small orifices to form filaments, which are thereafter quenched and collected. It is also known that, in order to show maximum utility for textile purposes, these filaments must be cold drawn to produce crystalline orientation along the fiber axis. Some of the polymers and the processing steps whereby they are converted to highly useful textile fibers are described in U.S. Patents 2,071,250, 2,071,251, 2,071,253, 2,130,948, and 2,465,319.

Most of the prior art processes have required that the filaments be extruded, quenched, and then wound onto a package after treatment with steam and/or an antistatic finish or the like. The package is then transferred to another machine where it is drawn from 3 to 6 or more times its original length, thereby orienting the fiber molecules. Such a two-stage process requires the use of two diiferent machines, and the requisite floor space to accommodate them. In addition, storage space is required for goods in transit from one operation to the other. Besides the obvious complexity of this two-stage process, it has been found that yarn properties not only vary depending upon the lag-time between the two operations, but also vary along the threadline due to uneven drawing, thereby introducing quality defects.

It has also been proposed to carry out the extruding and the drawing operation in a continuous process, whereby the functions of both machines are incorporated into one. This requires a set of mechanically driven rolls to withdraw the spun yarn from the extrusion apparatus, and forward it to a second set of driven rolls running at a higher peripheral speed than the first, whereby the bundle of filaments is stretched. It has been found desirable in both the one-stage and the two-stage process to use a snubbing pin, such as is described by Babcock in U.S. 2,289,232. This pin localizes the point at which the drawing action takes place. Localizing the draw point has been accepted as being necessary in order to produce yarn of uniform denier which is free of periodic variations in orientation. In addition, it is often necessary to provide other auxiliary equipment such as hot plates, ovens, steamers, rolls for applying finish, and the like, thus adding to the complexity of the operation.

It has now been found that in accordance with this invention, much of the complex processing equipment required in prior art processes can be eliminated, resulting in a simple, flexible process which produces a useful textile yarn in a single operation. Furthermore it has been found that, contrary to accepted theory, drawing need not be confined to a narrow zone in order to obtain a uniform product.

It is, therefore, an object of this invention to provide a process for continuously drawing a freshly-spun filament of molten synthetic linear polymer. A further ob- V ject is to provide a process for drawing a freshly-spun filament of molten polymer that is less complex and less costly than the prior art processes. A particular object of this invention is to provide a process for drawing a freshly melt-spun filament to provide an oriented filament which is more uniform than that obtained by prior art processes. Other objects will appear hereinafter.

The objects of this invention are attained by a process for preparing uniformly oriented textile yarn which comprises extruding a molten synthetic linear polymer from a spinneret to form filaments, quenching the filaments by cooling them to a temperature at least 50 C. below their melting point, drawing the filaments by passing them downwardly through a liquid drag bath whereby they are subjected to a continuously increasing tension while passing through the bath, and withdrawing them from the bath with the tension on the filaments being at least about 1.0 gram per denier as they leave the bath.

Surprisingly, and contrary to expected belief, yarns prepared by the process of this invention show a marked improvement in uniformity over yarns prepared by prior art processes. It is believed that the superior results are achieved at least in part by providing a drawing zone in which the yarn is subjected to a uniformly increasing tension, with the final tension attained remaining remarkably constant as drawing proceeds. It is most surprising that the final tension remains constant even when non-uniformities exist in the yarn being drawn.

This is in contrast to the prior art processes in which the yarn is elongated a fixed amount within a very narrow zone. In such processes, the tension on the yarn fluctuates with variations in denier, orientation, and the like along the thread line. In addition, the process of this invention provides a high degree of yarn temperature control within the drawing zone. It is well known that the actual temperature attained by a filament at the draw point markedly affects the properties of the drawn filament. In the process of this invention, each filament is completely surrounded by a liquid which may be readily maintained at a desired temperature. Due to the heat transfer characteristics of filaments prepared from synthetic linear polymers, the temperature of the filaments in the draw zone can therefore be readily controlled.

By melt-spun fiber is meant fibers formed from polymers which may be shaped by melting and extruding from fine orifices. Typical examples are the condensation polymers such as the polyesters and polyamides, and addition polymers such as polyethylene, polyvinylidene chloride, polyvinyl chloride, polystyrene, and the like. Melt-spun copolymers of all varieties are also included.

By quenching is meant the cooling of a molten filament from a temperature above its melting point to the solid state. At high speeds, air quenching will usually be desirable to cool the filaments from the as-spun temperature to one at least 50 C., and preferably C., below the melting point of said filaments, before contacting the liquid drawing bath. Suitable means for quenching include exposure to quiescent room temperature air, or preferably transversely directed air, such as described by Heckert in U.S. Patent 2,273,105. At lower speeds, quenchingby extruding the filaments into a body of a quenching liquid as described in Hull, U.S. 2,324,397 may be used. It is sometimes suitable to cool or quench the filaments by means of refrigerated air, inert gases (e.g., nitrogen and carbon dioxide), vapors, or fluid jets.

If a liquid quench is used, it is usually desirable to prevent extensive air quenching before the filament enters the liquid bath. Distances of less than 24 inches of quiescent air between the spinneret and the surface of the quench bath are usually used, with a preference for distances in the range of 2. to 6 inches. A liquid quench may generally be used at spinning speeds below about 3,000 yards per minute.

The use of a liquid quenching medium permits rapid cooling of the filaments. Fast quenching produces amorphous fibers, permitting linear orientation before crystallization. This provides a route to improved tenacity at low draw ratios. The liquid provides a uniform quench which improves the uniformity of the structure along the filament axis and from filament to filament. Additives ,may be included in this bath to modify the properties of the filaments.

In the process of this invention'the liquid provides lateral support to the filaments which'prevents interfilament sticking or fusing and allows a-closer hole spacing for increasing productivity per position for a given size spinneret or decreased spinneret size for a given productivity. It also provides axial support to the filaments which provides a continuous increase of tension along the filament axis with length of travelthrough the liquid and a rate of tension increase which may be controlled by the regulation of the viscosity of the quench liquid.

With reference to the accompanying drawings,

FIGURE 1 shows schematically an apparatus in which the process of the invention may be carried out at high speeds;

FIGURE 2 is a cross-sectional view of a preferred form of a modified draw tube 4 of FIGURE 1 for containing the drawing fluid;

FIGURE 3 shows a modified yarn-deflecting pin arrangement;

FIGURE 4 shows another embodiment of the liquid draw bath;

FIGURE 5 is a graph depicting the relationship between liquid height in the drawing bath and yarn windup speed from which suitable operating conditions to obtain a desired yarn elongation may be selected; and

FIGURES 6a and 6b are graphs showing a comparison of yarn uniformity of yarns prepared by the process of this invention and yarns prepared by a prior art process, respectively.

The process of this invention will be readily understood by reference to the drawings. In operation, linear polymeric material is melted and pumped through a filter bed as described by Greenewalt in US. Patent 2,217,743 (not shown in FIGURE 1), and is then extruded from spinneret 1 to form a plurality of filaments 2. The molten polymer is quenched by exposure to air in the space between spinneret 1 and the surface of the liquid 3, contained in draw bath 4. Preferably, quenching is accelerated by a current of air directed in streamline flow transversely of the threadline, as indicated by arrows 5. However, satisfactory results are obtained by using quiescent air.

The quenched filaments enter the draw bath 4, and leave via restricted orifice 6 in the bottom of the bath. The orifice is preferably made in ceramic material to resist abrasion by the yarn; it is conveniently inch in diameter, small enough to prevent excessive loss of liquid, but large enough to permit easy introduction of the yarn therethrough.

The individual filaments 2, converged to a single threadline 7, pass over a direction-changing pin 8. The purpose of this pin is to allow deflection of the threadline through an angle (a), which serves to separate entrained fluid 9, which falls into receiver 10 whence it is returned to the draw bath 4, via conduit 11, impelled by pump 12.

The yarn 7 ispulled through the liquid in draw bath 4!- by means of a pair of slightly axially-skewed pull rolls 13, 13 (driven by means not shown), about which it passes in multiple wraps. The yarn is delivered to wind up package 14, surface driven by contact with drive roll 15. Theyarn is traversed onto package 14 by means of reciprocating traverse guide 16'.

In operation, the height, viscosity and density of liquid in bath 4 are adjusted so that there is suflicient liquid .fromabout 1.8 to 2.6'grams per-denier being preferred),

on the yarn passing through the bath that the yarn is drawn (i.e., oriented) when pulled at a suitable speed (as explained hereinafter) by pull rolls 13, 13.

For maximum simplicity, in some cases it may be possible to dispense with pull rolls 13, 13, and use the Windup package 14- to supply the draw force. However, more satisfactory results are usually obtained with the arrangement shown in FIGURE 1, which avoids the necessity of winding the yarn under full drawing tension. Thus, the roll 15 may be driven at a suitably lower peripheral speed than rolls 13, 13, permitting a controlled relaxation of the drawn yarn. This is especially useful when processing polyamides and polyesters, which are preferably packaged at low tensions. 7

FIGURE 2 shows in schematic cross-section a preferred draw bath design, especially suitable for processing polyamides. The bath 4', with liquid surface at 3, contains a cylindrical wire screen 16, which surrounds the threadline (not shown) and rests on the inverted-conical bottom 17 of the bath. This structure is designed to minimize turbulence of the bath liquid, such turbulence having been found to be detrimental to yarn uniformity.

The yarn leaves draw bath 4 of FIGURE 2 via an orifice 6 in ceramic material as in FIGURE 1. Due to the rapid motion of the threadline through the bath,'a strong downward flow of liquid is induced; this flow is deflected to the outside of the bath by the inverted conical base 17 the displaced liquid rises again outside the wire screen 16, completing its circulation.

FIGURE 3'illustrates the use of multiple pins 8', 8', etc., which may be used instead of the single pin 8 of FIGURE 1. This arrangement is most suitably used when, for example, it may be desirable to reduce the vertical height of the unit; under these conditions, angle (a') may suitably be about 90, instead of 10 to 1 5 as shown in FIGURE 1. Alternatively, a single pin 8 may also be used when angle (a) is about 90; under these conditions, it is usually desirable to reduce the bath height somewhat to compensate for the increased snubbing drag around the pin. However, it is imperative that the liquid drag bath furnish the greater portion, i.e., at least about two-thirds, of the drawing tension, otherwise non-uniformities in orientation and denier appear in the drawn yarn.

FIGURE 4 shows an alternate draw bath arrangement which is particularly suitable'for processing yarn at lower speeds, e.g., about 750 to 3,000 yards per minute. Like parts have like numbers as in FIGURES 1 to 3.

Filaments 2 are extruded from spinneret 1, as in FIG- URE l. The filaments are quenched by air 5, and enter the draw bath 4" which is in the form of a long tube pump via conduit 18.

at position 3. The yarn leaves the draw'zo-ne through orifice 6.

7 Liquid may be supplied to tube 4" via catch basin 19 through inlet 20 by a pump (not shown), and thence pass downwardly through the tube, being returned to the If the direction of fluid flow is reversed to provide a countercurrent motion of yarn and fluid, considerable difficulty may be experienced since with 'countercurrent flow the velocity profile of the fluid is such as to force the filaments against the walls of the tube, thereby producing non-uniformities in the yarn. However, countercurrent flow at low velocities may be used.

It should be noted that the draw bath of this invention is readily adapted to heating and/or cooling in order to eifect' changes in viscosity, drag, rate of yarn crystallization, or the like. For example, steam coils may be'inserted in reservoir 10 (FIGURE 1), or may be wrapped around bath 4, 4 or tube 4"; alternatively, heat may be supplied by electric resistance tapes, radiant heat, or the like.

aeoasoe The practice of this invention limited by the following examples.

EXAMPLE I A spinning apparatus is set up substantially as shown in FIGURE 1. The distance from the surface of the drawing bath to the face of the spinneret is 2 feet. The depth of the iiquid in the drawing bath is 8 feet. The bath is heated by means of steam coils to the temperature shown herein below. The y-arn leaving the quench tubes is deflected through an angle (a) of about 90", passing over six Al Si .Mag (a ceramic material manu- :Eactured by the American Lava Company) pin guides arranged as shown in FIGURE 3. The yarn is collected directly on the windup bobbin, without the use of the yarn forwarding rolls 13, 13.

Polyethylene terephthalate is melted in the apparatus of Greenewalt (referred to hereinabove), and pumped through a filter to a 34-hole spinneret. The rate of throughput is 16 grams per minute and the spinneret temperature is about 290 C. The extruded filaments are quenched in ambient room temperature air during the two-foot passage from spinneret to surface of the drawing tube which contains water.

The properties of yarn spun under varying conditions is shown in Table 1. Denier per filament is given in column D, the tenacity (in grams per denier) in column T and the break elongation (in percent) in column E. Tension is measured (in grams per denier) as the filaments leave the bath.

TABLE 1.WINDUP SPEED, 750 YD. PER MIN.

is illustrated but not Polymer Yarn Properties After Through- Bath Tension Boiloff Sample put, gm./ Temp, (g.p.d.)

min. 0.

D T E From these data it is apparent that when processing polyethylene terephthalate filaments, an increase in bath temperature results in an increase in orientation; thus, the final product has a lower denier, higher tenacity, and lower break elongation at constant polymer throughp In order to show that the tension on the filaments as they leave the liquid bath is uniform, a spring-mounted knurled roll is substituted for the Al Si Mag pin guides. Angle (a) is 90. It is observed that the roll maintains a steady position as the filaments pass over it indicating that a high degree of tension uniformity is attained.

The data in Table 2 which follows is furnished to provide a scale for comparing certain of the physical properties of polyethylene terephthalate yarns prepared by the process of this invention with properties of similar yarns prepared by a hot-pin drawing process.

TABLE 2,-PROPERTIES 0F POLYETHYLENE TEREPH- THALATE YARN PREPARED BY HOT-PIN DRAWING PROCESS Tenacity Break Draw Ratio (g.p.d.) Elongation, percent EXAMPLE II Polyethylene terephthalate having a relative viscosity of 29 is melt spun asdescribed in Example I, with the space between the spinneret rface and the water being four inches, and the depth of the liquid bath being ten cfeeti Roll 14 is positioned directly under orifice 6 so that angle (a) is zero. Pin 8 and roll 13 are removed. The bath is held at a temperature of 88 C., and the yarn is wound up at 3,000 yards per minute. The tension on the yarn as it leaves the bath is 3.0 grams per denier.

'Ihe yarn collected is found to have a denier per filament of 4.1, a tenacity oi 7.7 grams per denier, and a break elongation of 20%.

EXAMPLE m Polyhexamethylene adipamide (i.e., 66-nylon) flake of 39 relative viscosity is melted as in Example I, and is:

extruded from a 13-hole spinneret at 18 grams per minute. The filaments are quenched by ambient air at room temperature (24 C.) while passing from spinneret to draw bath, a distance of 24 inches. The draw bath arrangement is similar to that in FIGURE 1, except that pin 8 is dispensed with; the threadline is deflected through angle (a) as it leaves the ceramic orifice 6. The orifice thus serves both as orifice 6 and pin 8. In this experiment, angle (a) is about 7"; the orifice is 5 inch in diameter.

Pull rolls 13, 13 have a peripheral speed of 5200 yards per minute; the yarn is allowed to retract about 7% before winding onto the package (14) at 4840 yards per minute. Forty denier yarn is obtained.

The liquid in the bath is water, and its temperature, after running for some time, is about 35 C., i.e., about 10" above room temperature. The temperature riseis produced by the heat of the yarn (filament temperature about -140" C. at the draw bath) plus heat generated in drawing. The height of the liquid in the draw bath, the tension on the yarn as it leaves the bath (in grams per denier), and the yarn break elongation at these heights and tensions are given in Table 3 below.

TABLE 3 Yarn Liquid Tension Break Sample Height (g.p.d.) Elonga- (inches) tion, percent The data in Table 4, which follows, is furnished to provide a scale for comparing certain of the physical- TABLE 4.)PROPERTIES OF (iii-NYLON YARN PREPARED BY COLD-PIN DRAWING PROCESS Break Draw Ratio Tenacity Elonga- (g. p.d.) tion, percent The following examples illustrate the surprising degree of uniformity obtained in yarns prepared by the process of this invention.

3,002 ,so g

7 EXAMPLE IV Restret ch modulus uniformity test -The measurement of uniformity of modulus at 4% stretch has been found to be a reliable measure of uniformity of strains and tensions residing in a yarn. The testused consists-of passing a significant amount ofyarn through a one .inlwhich the yarn is continuously stretched an additional 4% in length while measuring and recording the. tension. developed in the yarn in 'the stretching zone: The tension is conveniently recorded by means of a Zimmer electronic tensiometer. as described by De Riz in Measurement of Thread Tension-and its Use in Manufacturing Operations, Melliand Textilberichte, vol. 37, age. 13.7 95. T e can arriedt a p e of flwarr sne min 'rsst e h mo l profile for a'package' of yarn, is madeby plotting on a gnaph the range of-yalues observed during 5-minute intervals of testing versus the weight of yarn remaining on the pa ka e, v

l I3 lo n yarnv having 1 3-filaments and a total'denier of 40 prepared as describedin Example IIIusing a water depth of 13 inches in the draw bath. The yarn is tested foriuniformity using the restretch modulus test'described above andfound to have an average variation in modulus of 2.6 for 2800 yards of yarn. The surprising degree of uniformity attainedby the process of this invention becomes evident when it is realized that an equivalent commercially available nylon yarn, prepared by drawing on a pimexhibits an average variation in modulus of 5.6%. comparisonof. the. range of yalues obtainedin. consecutive 5-minute intervals of testing is shown in FIGURES 6a and'6b, which further points out an over-all drift in modulus through the package ofthe'commercial yarn whereas the yarn 'prepared by the processor the present. inventionshows substantially no driftin modulus. In'FIGURE. 6:: it can be seenthat there is substantially nomodulus drift for the yarn prepared by the process of this invention. Conversely, as shown in FIGURE 6b, the modulus drift for thepin -drawn yarnis quite great.

E MP E V Birefringence uniformity test The birefringence uniformity test consists of obtaining a series of 25 birefringence measurements 2 mm. apart on a single filament. The coeflicient of variation from the mean of the birefringence measurements is taken as an index of uniformity. Since birefringence isan indica: tion of orientation of. molecular structure, any improvement in the uniformity of birefringence indicates an improvement in uniformity of molecular orientation.

Polyhexamethylene adipamide is melted and extruded through a 13+holespinneretat about 16 grams per minute. After, passing through air for a distance 'of 24 inches, the filaments pass through a draw bath containing 5 /2 inches of water before being wound upat 4300 yards perminute. The equipment arrangement is similar to that of FIGURE 1, except that pin 8 is not used. Forty denier. yarn is obtained.

The yarn thus produced is tested for birefringence uniforrm'ty, as described above, and-found to exhibit a coitance gauge.

8 variation in denier electronically by means of a capac- Results are reported as percent variation on an arbitrary scale and give a relative rating of denier uniformity.

Nylon yarn is prepared substantially as described in used. and the rate of extrusion is adjusted to give a denier yarn. The height of the water. in the draw bath is 13 inches. The yarn produced is tested for denier uniformity, using the Uster evenness test described previ ously, and found to exhibit an average variation of 1.2%

(arbitrary scale). An equivalent yarn which had been drawn on a cold pin exhibits an average variation of 1.9%, which is clearly inferior to the yarnof this invention.

" EXAMPLE VII This example illustrates the effect of varying quenching conditions. The arrangement is that of FIGURE 1, except that no draw rolls are used; the yarn samples are wound, without relaxing, directly on the drive roll at 5000 yards per minute. The yarn is quenched with room temperature air directed transversely of the filaments at an average velocity of about 50 feet per minute. The

filaments are drawn in a water bath of 4-inch depth, 1 arranged as shown in FIGURE 2.

'Polyhexamethylene adipamide flake is melted as Example III, and extruded from a 34-hole spinneret at a rate of 35.5 grams per, minute to form 70 denier yarn at the stated windup speed. Quenchingdistance from spinneret to bath liquid, tension on the yarn asit leaves the bath, and the corresponding yarn properties are listed in Table 5. For convenience in making comparison, break tenacities in grams per denier at break have been calculated.

TABLE 5.QUEN CH BY TRANSVERSE AIR, 50 FTJMIN;

Yarn Properties Dis- Tension Tenacity 7 Sample tance, (g.p.d.) (g.p.d) Break 7 Inches Elonga- Break tion, Tenacity percent 33 2.0 4 6 36 6 3 30 2.0 4 6 37 6 3 24 2.0 4 5 3S 6 2 21 2.1 3 8 35 5 1 l8 2. 3 4 l 27 5 2 When the test is repeated, using ambient air, the fol-.'

lowing results are obtained:

TABLE 6.+QUENOH BY AMBIENT AIR This experiment shows that when the yarn is insufiiciently quenched before it enters the draw bath, both tenacity and elongation decrease, yielding a lower quality product. The transversely directed at is a more efiicient quenching medium than ambient air, as would be expected.

EXAMPLE VIII The draw bath of this invention is eminently suitable for processing yarn at very high speeds, as shownjbylthisl example.

' Polyhexarnethylene adipamide flake is melted and extruded from a 13-hole spinneret at a rate of 34 grams per minute. The apparatus arrangement'is that of-FlGURE attests 1, having a deflection angle (a) of 90 no draw rolls are used, the yarn samples being collected directly on roll 14.'

A 10-inch depth of water is used in the draw bath. The spinneret is positioned 24 inches above the surface of the water. At a Windup speed of 9000 yards per minute and a tension of 2.6 grams per denier as the yarn leaves the bath, 40 denier yarn with a tenacity of 6 grams per denier and 18% break elongation is produced.

The test is then repeated, replacing the water in the draw tube with liquid CClgF-CClFg, to a depth of 10 inches, increasing the pump speed to 49 grams per minute, and removing (by aspirating) 12 of the extruded filaments. The remaining single filament is drawn in the liquid draw bath and wound up at a speed of 13,100 yards per minute with a tension of 1.6 grams per denier on the filament as it leaves the bath; it has a tenacity of 3.7 grams per denier and a break elongation of 52%.

EXAMPLE 1X Polyhexamethylene adipamide flake of 35 relative viscosity is melted and extruded from a IO-holespinneret, following the procedure of Example III. The filaments are quenched by air moving at about 35 feet per minute, directed transversely to the threadline. The apparatus arrangement of FIGURE 1 is used, with a spinneret to bath distance of 24 inches, and a deflection angle of 90.

The filaments are drawn while passing through a 6-inch deep bath of the following composition, in parts by weight:

parts sorbitan monolaurate,

parts silicone oil of 50 centistokes viscosity (DC-200 fluid, manufactured by Dow Corning Corporation, Midland, Mich), and

85 parts purified kerosene The yarn passes over pin 8, and is deflected through a 90 angle. Pin 8 is of knurled cold-rolled steel. The drawing tension in the yarn is over 3.0 grams per denier, of which about 0.5 gram per denier is due to drag over the pin. The yarn is collected directly on Windup roll 15 at a speed of 6,365 yards per minute. Pull rolls 13, 13 are omitted.

The yarn denier is 34, and it has a tenacity of 6.0 grams per denier and a break elongation of 22%. When knitted into tubing and dyed, the resulting fabric is very uniform in the greige and dyed condition.

The foregoing examples have shown that textile filaments with a wide range of properties canbe produced by the process of this invention. It is, therefore, merely necessary to select the proper combination of conditions, chief variables being the Windup speed and the liquid head in the draw tube.

In the apparatus arrangement in which substantially all the drag is produced by the liquid in the draw tube, such as in FIGURE 1, when angle (a) is small (e.g., 5 to 15), it has been found that in order to produce 66- nylon of about 30% break elongation (a desirable range for many textile purposes), the relations in Table 7 can be used as a guide.

TABLE 7.RELATION BETWEEN LIQUID HEAD AND WINDUP SPEED At lower speeds a change in viscosity of the liquid would, of course, avoid the need for a relatively deep bath. In addition, a part of the tension could be supplied, as described in Example IX, by pin 8. However, if more than about one-third of the drawing tension is supplied by frictional contact with the pin, uniformity of the yarn drops olf and the advantages of using a liquid drag bath are lost.

When the process of this invention is used for orienting other melt-spun polymeric filaments, it is obvious that a different amount of drag will be required, depending on the drawing tension needed to satisfactorily orient the filaments. The determination of such tensions is well known to those skilled in the art. When such tension is known, the required relation between operating variables is determined by the following proportion:

T is proportional to V ,,0-2 :n.a o.4

where T=drawing tension V=yarn speed zviscosity of liquid =density of liquid h=head of liquid The proportionality constant is readily determinable from a single test with any given equipment arrangement.

EXAMPLE X efiect of varying quench bath temperature.

TABLE 8 Break Temperature C.) Tension Tenacity Elonga- (g.d.p.) (g. p.d.) tion (percent) The data in Table 9 show the effect of varying the distance from spinneret face to quench-draw bath. The

quench bath temperature is 94 C. and the filaments are wound up at approximately 1,000 yards per minute.

TABLE 9 Break Distance (inches) Tension Tenacity Elonga- (g.p.d.) (g.p.d.) t1on (percent) The data in Table 10 show the effect of varying windup speed. The distance from the face of the spinneret to quench-draw bath is 5 inches and the temperature of the bath is 93 C.

TABLE 10 Break Speed (yards per minute) Tension Tenacity Elonga- (g.p.d.) (g.p.d.) tlon (percent) As shown in Example VII, the degree of quenching before the filaments enter the liquid bath does afiect the.

These data show the yarn properties. This is particularly true at speeds of- 5,000 yards per minute and higher. It is thought that this may be due to the formation of a highly oriented filament skin and a relatively unoriented core when the hot filament contacts the fluid. Insufficient quenching may also cause the draw-bath liquid to boil, decreasing its effective height and creating a turbulence which appears to produce yarn non-uniformity, and may even cause the threadline to break. As a guide in selecting proper quench conditions, it is usually desirable to cool the filaments at least 50 C. and preferably 100 C. or more below the melting point of the polymer. For ex ample, 66-nylon, with a melting point of about 264 C.,' is preferably quenched to a temperature of at :least about 160 even better results are obtained when quenched to 120 to 140 C. Accordingly, when the filaments are quenched in the liquid bath, the speed and depth of the bath must be regulated to provide quenching to the aforementioned temperatures before any appreciable drawing takes place. It is also imperative that the spinneret face not be in contact with the surface of the bath since contact with the bath would, depending on the relative ternperatures of the bath and the spinneret, either result in freezing thepolymer in the spinneret or preventing proper quenching. I

As previously disclosed, it may sometimes be desirable to heat the bath to promote ease of drawing. Although heating reduces the available drag from a given liquid head, usually the drawing tension required to obtain specified yarn properties will be reduced to an even greater extent, permitting a lower bath height.

T heorifice in the bottom of the draw bath should be made of some abrasion resistant material, such as chromeplated steel, sintered carbides, sapphire, or prefer-ably ceramic such as fused alumina, titania, or the like. The orifice is preferably small, to minimize the amount of liquid carried down through it. It must, however, be large enough to permit stringup, which is usually accomplished using' an aspirating gun. A suitable size for the orifice is to inch in diameter.

The pump for recirculating entnained bath fluid should have provision for maintaining constant head in the bath, so that all yarn will be drawn under uniform conditions. The liquid circulating system should also be adapted to empty the draw bath for casein yarn stringup.

The preferred liquid for the draw bath is water. However, other materials such as minor amounts of wetting agents, antistatics, fugitive tints, textile finishes, or the like, may be added as desired. Organic liquids which are no-nsolvents for the polymer may also be used, as pure compounds, mixtures or aqueous solutions. Compounds with a swelling effect are sometimes desirable. In addition, solutions of inorganic salts, acids or bases may be employed.

It is important that the liquid composition selected for the draw bath be nonfoam-ing under the operating conditions. Considerable air is entrained with the running threadline, and with some reagents a stable foam develops which impedes spinning. v

The process of this invention may be carried out over a wide-range of windup speeds, limited only by the need to provide a liquid draw bath with adequate drag to draw the filament. In general, the yarn must be withdrawn from the bath at-a speed of at least about 750 yards per minute in order to-achieve any-appreciable orientation. For polyamides, it is preferred that the windup speed be at least 3,000 yards per minute. The upper limit is set primarily by mechanical equipment limitations, and hence is not areal limit for the process ofthis invention.

The process of this invention is highly useful in that it provides, in a single operation, means for producing uniformly oriented filaments from melt-spun polymers. The physical properties of filaments produced may'be readily controlled by a change in height composition, or

1'2 temperature of the bath without the 'needffor making mechanical alterations, e;g., gear changes, required to effect changes in draw ratio when usingconventional drawingequipment.

Theprocess can-be carried out at very high yarn speeds, of'the order of 750 to 13,000 or more yards per minute, exceeding speeds heretofore attained. The apparatus required for the process of this invention is so simple and compact that it requires less space than was formerly needed to merely form the melt-spun filaments. Thus the drawing machine formerly required maybe eliminated, along with the plant area 'in which it was installed. The result is, therefore, a large reduction in cost of manufacture, and in plant'investment.

Theiproperties of the products obtained by the process of this invention may be modified, if desired, by subsequent after-treatments, such as stress-relaxation, or the introduction of additional orientation and higher tenacity through the use of mechanical draw. As another example, curly or crimped yarns can be prepared by introduction of non-uniformities in the structure, such as by frictional contact on one side 'of the filament only, followed'by a relaxation step.

Yarn produced by the process .of this invention has greater property uniformity from package to package, and also along its length.' The package-to-package improvement is thought to result from eliminating the lag period (which may .change according to manufacturing schedules) between the spinning and drawing stages of the conventional process. In addition, variable drawing due to changes resulting from'wean'build up of deposits,

and the like on draw pins used in the conventional process, are eliminated.

The improvement in short-range uniformity is thought to be due to the intimate and uniform contact between bath liquid and individual filaments, resulting in the uniform application of drag, which provides a uniform drawing tension on each filament. Conventional drawing between rolls, over snubbing pins or other frictionproducing surfaces, necessarily involves, at best, contact between only one side of each filament and-the heated (by friction or otherwise) surface. At worst, the filaments bundle may remain compacted 'so that some filaments do not even contact the snubbing surface. In addition, the chance of mechanical slippage of the feed rolls is eliminated, as well as process interruptions due to formation of wraps on the feed rolls. In addition, irregular sections along the filament line will not draw uniformly since the elongation must take place in afixed zone. In contrast, by the processof this invention an increase in surface area of the filament results in a corresponding increase in the liquiddrag, thereby producing an oriented filament of high uniformity.

Although the :process of this invention has been described in terms "of producing a continuous filament yarn, it 'is also useful'for producing a staple; .for such production, a'high speed cutter, .e:g., a Beria or a flying knife cutter, may'be substituted for windup rolls 14, 15.

The process of this invention is highly useful in orienting filaments offreshly-spun linear polyamides, especially polyhexamethylene adipamide and polycaproamide. The preferred class of polyamides are those prepared by reacting diamines and dicarboxylic acids (or their amidefonming derivatives), or by reacting w-amino acids (or their amide forming derivatives). 'Such polymers are characterized 'by recurring II I a link forming a part of the polymer chain.

Polyesters preferred for the process of this invention are those disclosed by Whinfield and Dickson in US. Patent 2,465,319, and are prepared by the reaction between .glycols and van esterof terephthalic acid.

In general, polymers suitable for the practice of this invention are those polymers of linear molecular structure which may be melted and extruded as filaments, and subsequently oriented by cold drawing to yield crystalline fibers. In addition to the polymers listed hereinabove, there are included fiber-forming condensation polymers such as polyureas, polyurethanes, polyethers, polyacetals and their copolymers; melt-spinnable addition polymers such as polyethylene, polyvinylidene chloride, the polyvinyl halides, the polyvinyl esters (acetate, butyrate, etc.), polystyrene, polymeric esters of acrylic and methacrylic acids (e.g., polymethyl methacrylate), acrylonitrile and fiber-forming copolymers thereof.

It will be apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. The process for preparing uniformly oriented textile yarn which comprises extruding a molten synthetic linear polymer from a spinneret to form filaments, quenching said filaments to provide a solid structure by cooling them to a temperature at least 50 C. below their melting point, subjecting said filaments to a continuously increasing drawing tension by passing said filaments downwardly through a liquid drag bath, maintaining said bath at a temperature to preserve said solid structure, withdrawing said filaments irom said bath at a speed of at least 750 yards per minute, said tension being at least 14 about 1.0 gram per denier as said filaments leave said bath.

2. The process of claim 1 wherein said filaments are withdrawn from said bath at a speed of from about 3,000 to 6,500 yards per minute.

3. The process of claim 1 wherein said filaments are withdrawn from said bath at a speed of at least about 3,000 yards per minute.

4. The process of claim 1 wherein said liquid bath is water.

5. The process of claim 1 wherein said polymer is a linear fiberfor-ming polyester.

6. The process of claim 1 wherein said polymer is a linear fiber-forming polyamide.

7. The process of claim 1 wherein said filaments upon leaving the bath are deflected through an angle of about 5 to 8. The process of claim 1 wherein said tension is from about two to three grams per denier.

References Cited in the file of this patent UNITED STATES PATENTS 1,871,100 Walton et al. Aug. 9, 1932 2,054,852 Dreyfus Sept. 22, 1936 2,289,232 Babcock July 7, 1942 2,323,383 Dreyfus July 6, 1943 2,511,699 Drisch et a1 June 13, 1950 2,604,689 Hebeler July 29, 1952 2,705,183 James Mar. 29, 1955 

1. THE PROCESS FOR PREPARING UNIFORMLY ORIENTED TEXTILE YARN WHICH COMPRISES EXTRUDING A MOLTEN SYNTHETIC LINEAR POLYMER FROM A SPINNERET TO FORM FILAMENTS, QUENCHING SAID FILAMENTS TO PROVIDE A SOLID STRUCTURE BY COOLING THEM TO A TEMPERATURE AT LEAST 50*C. BELOW THEIR MELTING POINT, SUBJECTING SAID FILAMENTS TO A CONTINUOUSLY INCREASING DRAWING TENSION BY PASSING SAID FILAMENTS DOWN- 